Half-metallicity in two-dimensional Co ₂ Se ₃ monolayer with superior mechanical flexibility

Abstract Pursuing two-dimensional (2D) intrinsic ferromagnetism with high Curie temperature and great mechanical flexibility has attracted great interest in flexible spintronics. In the present work, we carried out a density functional theory (DFT) investigation on the 2D M ₂ Se ₃ ( M = Co, Ni, and Pd) monolayers to understand their structural stabilities, electronic, magnetic and mechanical properties. Our results show that the Co ₂ Se ₃ monolayer exhibits a fascinating half-metallic ferromagnetism with high Curie temperature (~600 K). In addition, due to their unique buckling hinge-like structure, M ₂ Se ₃ monolayers possess the large out-of-plane negative Poisson’s ratio (NPR) and superior mechanical flexibility evidenced by their unusual critical strain (~50%–60%) two times greater than the well-known 2D materials. These findings imply that 2D M ₂ Se ₃ family is the promising materials for the applications in the flexible and high-density spintronic nanodevices.